Searching for an object in an unknown NSDictionary/NSArray depth

Question

I've already asked a similar question but this is slightly different so i Thought it would be fine to ask another question.

I'm storing Arrays within Arrays, as well as NSDictionaries. It's a utility kind of application and there is no set structure, the user can enter nested information as much as they require.

I need a method that can scroll through the entire contents of an Array/Dictionary and return the specific dictionary based on a value that I send the method. Here's an example..

NSMutableArray *array = [[NSMutableArray alloc]init];

NSMutableDictionary *enteredItem = [[NSMutableDictionary alloc]init];

[enteredItem setObject:@"i'm a title"       forKey:@"title"];
[enteredItem setObject:@"i'm an id"         forKey:@"id"];
[enteredItem setObject:@"i'm a description" forKey:@"description"];
[enteredItem setObject:@"i'm a timestamp"   forKey:@"timestamp"];
[enteredItem setObject:array                forKey:@"items"];

[array addObject:enteredItem];
[array addObject:anotherDictionary];
[array addObject:moreDictionaries];

So in the example above, I would need to find (return) the dictionary that contains "i'm an id".

The similar question I asked is located here.. Searching for a value in an unknown NSMutableArray depth - I'm having trouble returning a dictionary and also comparing the object.

Hopefully my question is clear. Thanks for any help you can offer.

score 4 · Accepted Answer · edited May 23 '17 at 12:34

Continuing from the answer, you need to do some modification:

- (id)findDictionaryWithValue:(id)value inArray:(NSArray *)array
{
    __block id match = nil;
    [array enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
        if ([obj isKindOfClass:[NSArray class])
        {
            match = [self findDictionaryWithValue:value inArray:obj];
        }
        else if ([obj isKindOfClass:[NSDictionary class])
        {
            match = [self findDictionaryWithValue:value inDictionary:obj];
        }
        *stop = (match!=nil);
    }];
    return match;
}

- (id)findDictionaryWithValue:(id)value inDictionary:(NSDictionary *)dict;
{
    __block id match = nil;
    [dict enumerateKeysAndObjectsUsingBlock:^(id key, id obj, BOOL *stop) {
        if([obj isEqual:value]) {
            match = dict;
        } 
         else if ([obj isKindOfClass:[NSArray class])
        {
            match = [self findDictionaryWithValue:value inArray:obj];

        }
        else if ([obj isKindOfClass:[NSDictionary class])
        {
            match = [self findDictionaryWithValue:value inDictionary:obj];
        }
        *stop = (match!=nil);
    }];
    return match;
}

NSDictionary *resultDict = [self findDictionaryForValue:@"i'm an id" inArray:array];

However, you must be careful with recursion. If there is any circular path, you will get an infinite loop( and stack overflow before crash).

Thanks, will try it out. Shouldn't the end of an NSDictionary/NSArray signal the end of the recursion? — user1168056, Jan 29 '12 at 20:30
Just tested the code and unfortunately It doesn't find it. I'm logging the dictionaries it's detecting (that it's sending to the function) and it stops cycling through the array of the dictionaries after the first entry. I'm trying to figure it out. — user1168056, Jan 29 '12 at 21:00
Hi, thanks for your help. I think it might be missing.. id object = [dict objectForKey:subKey]; or did you intend for 'obj' to be used? Thanks :) — user1168056, Jan 29 '12 at 21:42
Ok, cheers for your help. It's doing the same thing, unfortunately. As soon as it hits an array of dictionaries it stops looking after the first entry. — user1168056, Jan 29 '12 at 21:49
Just tried the latest edit, it works! Thanks so much for your help! — user1168056, Jan 29 '12 at 23:14

Searching for an object in an unknown NSDictionary/NSArray depth

1 Answers1